1. Field of the Invention
The present invention relates to a detection system, a detection method and a detection program product for detecting an object present in a given observation area.
2. Description of the Related Art
It has been a conventional practice that a plurality of receivers are installed in an area such as an event hall, and a walker who moves around in the area carries a transmitter so that a position of the walker can be estimated. Receivers of the area detect a transmitted signal sent from the transmitter. Each receiver transmits information obtained from the transmitter by radio or cable to a certain position detection system. A position detection system and a position detection method have been disclosed which can detect a position of a moving object such as a walker by using a mobile communications system in this way.
For example, in an observation area 126 to be observed, as shown in FIG. 1, a transmitted signal sent from a transmitter 121 carried by a walker 122 is received by receivers 120a, 120b, . . . , and 120e, and is relayed to a position detection system through a communications network 125. Accordingly, a position of the walker can be detected. By designating a detection range of the receiver 120a as an area A, a detection range of the receiver 120b as an area B, . . . , and a detection range of the receiver 120e as an area E, it is possible to recognize a movement of the walker 122, for example, from the area E, the area A, the area B, the area C to the area D through the receivers 120a, 120b, . . . , 120e in FIG. 1. In this case, the ranges detectable with the respective receivers must be adjusted depending on the state of receiving transmitted signals in accordance with a surrounding physical environment thereof. As shown in FIG. 2, when a crossover region 127 takes place between the areas C and D, a change in intensity of a signal transmitted from a transmitter or the like caused by a direction of the body of the walker may lead to a false position recognition because both of the two receivers 120c and 120d are allowed to receive the transmitted signal. Thus, it is undesirable to create an area, which can be sensed by a plurality of receivers. When a man judges there is crossover area, detection ranges must be arranged so as not to create any crossover area by adjusting each receiver.
Meanwhile, when a disaster occurs in the observation area, it is necessary to instantly determine whether or not there is a walker near the disaster site. For example, in FIG. 1, when a man judges the entire observation area 126 is dangerous, coverage by all the receivers 120a, 120b, . . . , 120e must be maximized to judge whether no walkers are present in the observation area 126. Heretofore, however, it has been difficult to instantly switch the coverage by the plurality of receivers in response to such a situation.
Conventionally, when coverage by the receivers is adjusted, a man judges the present situation, and adjusts each receiver.